Organ walls are composed of several layers: the mucosa (the surface layer), the submucosa, the muscularis (muscle layer), and the serosa (connective tissue layer). In gastrointestinal, colonic, and esophageal cancer, e.g., small polyps or cancerous masses may form along the mucosa and often extend into the lumens of the organs. Conventionally, that condition is treated by cutting out a portion of the affected organ wall. This procedure, however, may cause extensive discomfort to patients, and poses health risks. Recently, physicians have adopted a minimally invasive technique called endoscopic mucosal resection (EMR), which removes the cancerous or abnormal tissues (polyps), keeping the walls intact.
In some cases, EMR may be performed with an endoscope, which may be a long, narrow elongate member equipped with a light, video camera, and other instruments. During EMR, the endoscope is passed down the throat or guided through the rectum to reach an abnormality in the affected organ. In some procedures, the EMR device is further equipped with a dissection device such as a wire loop, which is passed through an endoscopic channel extending up to the cap towards the polyp. Once there, suction is applied to the elongate member, which draws the polyp towards the endoscope cap. When the polyp is sufficiently drawn into the cap, the wire loop closes around the polyp, resecting it from the organ wall. Alternatively, a band may be placed around the tissue to accomplish resection or necrostasis. Subsequently, excised tissue may be extracted for examination, biopsy, or disposal. The tissue or polyp cauterization process may be accomplished by any know cautery or dissection tool.
Certain polyps, such as pedunculated polyps, are characterized by a stalk attached to the mucosal layer. Drawing such polyps into the cap without drawing in any other tissue is readily accomplished. Certain other polyps, such as sessile polyps, however, exhibit a broad base and they lay flat on the mucosal surface, devoid of a stalk. It is often difficult to grasp these polyps without drawing in a part of the muscularis layer.
In addition, the depth of the cut made by a wire loop cautery is critical. As discussed above, if the cut is too deep, the muscularis layer may be injured, which may cause a perforation. Conversely, if the cut is too shallow, the procedure may not remove enough of the affected tissue, which can require additional procedures, or worse, result in the development of metastatic cancer. Typically, more than 2 mm of cancer clearance is required to assure complete removal. EMR, as performed with conventional devices and methods, may result in complications such as perforation, bleeding, and/or strictures.
Therefore, there exists a need for an improved endoscopic mucosal resection tool that effectively resects both pedunculated and sessile polyps without damaging the surrounding tissue or muscle layers of the organ.